1. Field of the Invention
The present invention relates to a device for the formation, by pyrolysis, of a coating of metal or metal compound on one face of a moving hot glass substrate by bringing said face into contact with a gaseous reagent, comprising support means for conveying the substrate through a coating chamber, means for supplying and distributing reagent gas to the coating chamber and means for discharging exhaust gas from the coating chamber, and a method for forming a coating of metal or metal compound on a moving hot glass substrate by pyrolysis of a reagent in the gaseous phase.
The coating of metal or metal compound formed on a hot glass substrate by pyrolysis is used for modifying the apparent colour of the glass and/or presenting other properties required vis-a-vis incident radiation, for example the property of reflecting infrared. A single coating on the glass substrate may be used for these purposes, or a multi-layer coating. Examples would be coatings of tin oxide SnO.sub.2, tin oxide SnO.sub.2 doped with fluorine, titanium dioxide TiO.sub.2, titanium nitride TiN, silicon nitride Si.sub.3 N.sub.4, silica SiO.sub.2 or SiO.sub.x, alumina Al.sub.2 O.sub.3, vanadium pentoxide V.sub.2 O.sub.5 or tungsten oxide WO.sub.3 or molybdenum oxide MoO.sub.3, and in general oxides, sulphides, nitrides or carbides and a layering of two or more of these coatings.
The coating can be formed on a sheet of glass which moves in a tunnel oven or on a glass ribbon during formation, whilst it is still hot. The coating can be formed inside the lehr which follows the glass ribbon forming device or inside the float tank on the top face of the glass ribbon whilst the latter is floating on a bath of molten tin.
2. Description of the Related Art
To form the coating, the substrate is brought into contact, in a coating chamber, with a gaseous medium comprising one or more substances in the gaseous phase. The coating chamber is fed with a reagent gas through one or more slots, the length of which is at least equal to the width to be coated, fed through one or more ejection nozzles. Depending on the type of coating to be formed and the reactivity of the substances used, if several substances have to be used, these are distributed either in the form of a mixture by a single ejection nozzle in the coating chamber via a slot, or separately by several ejection nozzles via separate slots.
Methods and devices for forming such a coating are described for example in French patent No 2 348 166 (BFG Glassgroup) or in French patent application No 2 648 453 A1 (Glaverbel). These methods and devices lead to the formation of particularly strong coatings with advantageous optical properties.
However, it is difficult by this technique to form coatings which are uniform across the width of the substrate, when the substrate is a large surface, such as the surface of a ribbon of float glass moving at a relatively high speed. A lack of uniformity is then found in the distribution of this coating over the entire surface of the substrate to be coated, which results for example in alternating streaks, the visual appearance of which, mainly in reflection, is different either in colour or in the degree of reflection.